Low Doses of Ethanol Reduce Evidence for Nonlinear Structure in Brain Activity

Abstract

Recent theories of the effects of ethanol on the brain have focused on its direct actions on neuronal membrane proteins. However, neuromolecular mechanisms whereby ethanol produces its CNS effects in low doses typically used by social drinkers (e.g., 2-3 drinks, 10-25 mM, 0.05-0.125 gm/dl) remain less well understood. We propose the hypothesis that ethanol may act by introducing a level of randomness or "noise" in brain electrical activity. We investigated the hypothesis by applying a battery of tests originally developed for nonlinear time series analysis and chaos theory to EEG data collected from 32 men who had participated in an ethanol/placebo challenge protocol. Because nonlinearity is a prerequisite for chaos and because we can detect nonlinearity more reliably than chaos, we concentrated on a series of measures that quantitated different aspects of nonlinearity. For each of these measures the method of surrogate data was used to assess the significance of evidence for nonlinear structure. Significant nonlinear structure was found in the EEG as evidenced by the measures of time asymmetry, determinism, and redundancy. In addition, the evidence for nonlinear structure in the placebo condition was found to be significantly greater than that for ethanol. Nonlinear measures, but not spectral measures, were found to correlate with a subject's overall feeling of intoxication. These findings are consistent with the notion that ethanol may act by introducing a level of randomness in neuronal processing as assessed by EEG nonlinear structure.

Temporal asymmetries of short-term heart period variability are linked to autonomic regulation

“…The second aim is to link the presence of these asymmetric patterns to the amplitude of sympathetic modulation. R-R variability series recorded from healthy humans during graded head-up tilt will be utilized to assess whether the contemporaneous increase of sympathetic modulation and decrease of vagal one (3,7,13,18) is responsible for a more pronounced presence of these temporal asymmetries.In this study, we will exploit three indexes devised to detect irreversible dynamics (6,9,17). In the APPENDIX, we will derive them according to a unique framework based on the representation of the dynamics in the two-dimensional phase space (R-R(i),R-R(iϩ)), and we will summarize the relationship between time irreversibility, pattern asymmetry, and nonlinear dynamics.…”

A hybrid method based on time–frequency images for classification of alcohol and control EEG signals

“…It can be notice from Table 3, that our proposal yielded a better accuracy than the existing methods. [15] Correlation dimension Discriminant analysis 88% Kannathal et al [16] CD, LLE, entropy, H Unique ranges 90% Acharya et al [18] ApEn, SampEn, LLE, HOS SVM with poly kernel 91.3% Faust et al [19] WPD …”

“…Correlation dimension used as measures to discrimination of alcohol and normal EEG signals [15]. Chaotic measures are used as features to alcoholic from normal EEG signals [16].…”

On Episode Sensitization in Recurrent Affective Disorders: The Role of Noise

“…Neurons in the brain are subjected to various noise sources such as, among others, membrane potential fluctuations, synaptic noise, or random background activity. Moreover, noise sources cannot be assumed as constant as they might change because of altered neuronal function associated with different disease states or possibly as a result of psychopharmacological interventions (Ehlers et al, 1998;Huber et al, 1998). Moreover, a magnitude of studiesFreaching from the molecular up to the behavioral levelFshowed that noise cannot be simply regarded as a nuisance but can qualitatively change the behavior of a given system (eg Bezrukov and Vodyanoy, 1995;Astumian et al, 1997;Douglass et al, 1993;Braun et al, 1994;White et al, 1998;Gluckman et al, 1996;Rudolph and Destexhe, 2001;Simonotto et al, 1997;Winterer et al, 1999;Russell et al, 1999).…”

“…Hence, it will be interesting to see whether the described principles do apply to kindling and sensitization in experimental preparations. Experimental evidences already exist, which demonstrate that the drug ethanol acts by introducing randomness or 'noise' in neuronal processing (Ehlers et al, 1998) and, speculation so far, such pharmacologically altered neuronal noise sources could also effectively interact with neuronal sensitization processes. This example further indicates the need to understand noise-mediated behaviors in neurobiology not only with respect to normal brain function but in particular regarding pathophysiological and clinical consequences.…”